LONGITUDINAL MODE NOISE CONVERSION BY ATOMIC VAPOR

An external cavity diode laser with very low levels of amplitude noise is shown to have considerable amounts of frequency noise at the longi tudinal mode spacing frequency. This noise is observed by tuning the l aser near to resonance with an atomic vapour and measuring the transmi ssion of the vapour with a photodiode. The measured noise is enhanced by more than two orders of magnitude at the longitudinal modespacing f requency by conversion of frequency noise to amplitude noise by the va pour. The frequency noise was also simulated using intracavity electro optic modulation.